Apparatus for producing coordinated,simultaneous actuation of multiple rams



NOV. 4. 1969 mxo ET AL 3,476,016 APPARATUS FOR PRODUCING COORDINATED, SIMULTANEOUS ACTUATION OF MULTIPLE RAMS Filed Oct. 20. 1967 Hg. 2 INVENTOR- MAX. FREY DONALD M. FALLST TOM E. DIXON HLLys 7pm, *WW

United States Patent U.S. Cl. 91-411 1 Claim ABSTRACT OF THE DISCLOSURE Load pusher apparatus with two rams for actuating a pusher member in the apparatus, the rams being arranged for coordinated, simultaneous actuation. A first conduit is provided connected to the head end of one ram, a transfer conduit interconnects the rod end of the one ram and the head end of the other ram, and a third conduit connects to the rod end of the other ram. With fluid supplied the one ram through the first conduit to actuate the ram, captive fluid in the one rams rod end transfers to the head end of the other ram causing the other ram to be actuated. The two rams are connected to the pusher member in such a manner that the rams on actuation move opposite pusher sides an equal amount, thus to prevent skewing. The apparatus further includes, in the piston of each ram, a fluid passage opening onto opposite sides of the piston, and a valve inhibiting fluid flow through the passage from the rod end to the head end of the ram While permitting flow in the reverse direction. In this way exhausting or replenishing of the captive fluid is permitted, whereby the volume of the captive fluid remains substantially constant.

The present invention relates to the operation of fluidoperated rams, and more particularly to apparatus for producing coordinated, simultaneous actuation of at least a pair of such rams. The preferred embodiment of the invention described herein has to do with a load pusher attachment for a lift truck, where two rams are utilized to cause equal movements in opposite sides of a pusher member in the attachment, with reduction of any tendencies of the pusher to skew in the attachment.

A common form of load pusher apparatus includes a frame, a pusher member mounted for movement toward and away from the front of the frame, and a pair of fluid-operated rams which are operated simultaneously to move the pusher member. For such equipment to function properly, obviously the rams must extend and contract evenly in order to avoid undesirable skewing of the pusher member and binding of various other parts of the equipment. However, in known means for actuating rams in such equipment, ram coordination has often been poor.

A general object of the present invention, therefore, is to provide, in an organization including at least a pair of fluid-operated rams, novel apparatus for producing coordinated, simultaneous actuation of such rams.

More particularly, an object of the invention is to provide such apparatus which includes means controlling fluid flow to and from the rams whereby the rams, during their simultaneous operation, extend and contract evenly.

To accomplish these objects, the apparatus contemplated herein includes a first conduit for carrying fluid to and from the head end of one of the rams, a transfer conduit connecting the rod end of the one ram to the ICC head end of the other ram for accommodating fluid transfer between the rams, and a third conduit for carrying fluid to and from the rod end of the other ram. The pistons of the rams are so sized that the effective piston area exposed to the rod end of the first-mentioned ram is substantially equal to the effective piston area exposed to the head end of the second-mentioned ram. With such a construction, fluid in the rod end of the first-mentioned ram, in the transfer conduit, and in the head end of the second-mentioned ram constitutes a captive fluid acted upon by, and acting on, the pistons of the rams, to produce simultaneous like movement of the pistons.

A further and related object of the invention is to provide novel means for automatically maintaining the volume of such captive fluid constant, regardless of any specific gravity change resulting from a change in temperature, or other factor such as leakage, which could alter the original volume of the captive fluid. Such a provision is important in insuring proper coordination of the rams. Thus the invention features, in the piston of each ram, a novel organization of a fluid passage opening onto opposite sides of the piston, and valve means inhibiting fluid flow through the passage in one direction while accommodating such flow in the reverse direction, with the flow direction being such as to bring about replenishing or exhausting of captive fluid, as needed.

Yet another object of the invention is to provide apparatus of the type so far described which is relatively simple in construction and reliable in operation.

These and other objects and advantages attained by the invention will become more fully apparent as the description which follows is read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a simplified top plan view illustrating load pusher apparatus as contemplated by the invention, with a pair of hydraulic rams operable to extend a pusher member in the apparatus when actuated;

FIG. 2 is a schematic diagram illustrating the rams and other hydraulic components in the hydraulic circuit for the rams.

Turning now to the drawings, and referring first to FIG. 1, indicated generally at 10 is load pusher apparatus of the type adapted for attachment to the front of a lift truck. The pusher includes a frame 12 and a pusher member 14 which is movable toward and away from the front of the frame. The pusher member may have a substantially rectangular outline, viewing it from the front, and is disposed in an upright position, with the front substantially perpendicular.

The pusher member is mounted on the frame for movement toward and away from the latter through a pair of foldable arm assemblies 16, 18. Arm assembly 16 is disposed above assembly 18, and includes an inner arm part 16a pivotally connected at 20 to an outer arm part 16b. The inner end of part 16a is anchored to an elongated upright tube 22 which is journalled on an upright elongated pin 24 suitably mounted on frame 12. The outer end of part 16b is slidably mounted on pusher member 14, adjacent the right side thereof in FIG. 1, through an elongated upright pin 26 suitably secured to the outer end of the arm part, which pin is slidably received in a pair of opposed, vertically-spaced channel pieces, such as channel piece 28, mounted on the pusher member.

Arm assembly 18 is similar in construction to assembly 16 with inner and outer arm parts 18a, 18b, respectively, mounted in a similar manner on frame 12 and member 14, respectively. Thus, part 18a has its inner end anchored to a tube 27 which is journaled on a pin 29 mounted on the frame, and its outer end pivoted to part 18b through a pin 31. The outer end of part 18b is slidably mounted on pusher member 14 in a manner substantially the same as that shown for the outer end of arm part 16b.

The outer arm parts of the arm assemblies are pivotally connected together through a suitable pivot pin 30. Part 16b, in addition, is connected to frame 14 through a link 32 having one end pivoted at 34 to arm part 1612 and the other end pivoted at 36 to the pusher member. Link 32 prevents member 14 from shifting laterally relative to the frame.

Details of a similar pusher member mounting are described in a copending application of Donald M. Faust entitled Folding Arm Assembly for a Load Pusher, filed July 17, 1967, Ser. No. 653,695.

A pair of hydraulic rams 38, 40 are provided for shifting the pusher member toward and away from the front of the frame. Ram 38 has its cylinder 38a pivotally connected to frame 12 through an upright pivot pin 42 suitably mounted on a pair of vertically-spaced, parallel plates 44, 46 that form part of the frame. The rod 38b of the ram is pivoted at 48 to a crank 50 which is suitably anchored to previously-mentioned tube 22. Similarly, ram 40 has its cylinder pivoted to plates 44, 46 of the frame through a pin 52. Its rod is pivoted at 54 to a crank 56 which is anchored to tube 27.

On extension of the rams the arm assemblies unfold with shifting of the pusher member forwardly away from the frame. Contraction of the rams causes the reverse operation.

Turning now to FIG. 2, and further considering the rams, ram 38 includes inside its cylinder a piston 58 joined to the inner end of its rod. The piston includes opposite sides 58a, 5812 which face toward what are referred to herein as head and rod ends, respectively, of the ram. The surface areas of sides 58a, 58b constitute opposing effective piston areas of piston 58. Side 58a has a greater area than that of side 58b, due to the lack of any piston rod projecting from the side.

Provided in piston 58 is a bore 60 which extends downwardly part way into the piston from side 5812. The base of bore 60 communicates with an aligned bore 62 of somewhat reduced diameter which opens onto side 58a. Bores 60, 62 are referred to herein collectively as means defining a fluid passage opening onto opposite sides of the piston.

Seated at the base of bore 60, and closing off the upper end of bore 62 is a ball, or valve means, 64 having a diameter somewhat smaller than the diameter of bore 60. The ball is urged against the base of bore 60 by means of a biasing spring 66 the lower end of which acts against a ring 68 seated on the ball, and the upper end of which seats against a plug 70 screwed into the upper end of bore 60. Plug 70 is provided with an axial bore 70a which opens onto the upper side of the piston and also opens to the interior of bore 60. Spring 66 is so chosen that with fluid at normal operating pressures acting on side 58a of the piston, and hence on the base of ball 64, the ball remains seated in the position shown.

The head and rod ends of the cylinder of ram 38 are provided with ports 72, 74, respectively, for admitting hydraulic fluid to and exhausting it from the ram. The rod end of ram 38 is also provided with a bleeder screw 78 which is screwed into a suitable bore provided in the cylinder.

Ram 40 is similar in construction to ram 38, and includes in its cylinder a piston 80 joined to the inner end of the rod of the ram. Piston 80 includes opposite sides 80a, 80b facing the head and rod ends, respectively, of the ram. The surface areas of sides 80a, 80b constitute opposing effective piston areas of piston 80. The piston is so sized that the elTective piston area of side 80a is substantially the same as effective piston area of side 80a is substantially the same as the effective piston area of previously-mentioned side 58b, and less than the area of piston side 58a.

Provided in piston are a pair of aligned bores 82, 84, which correspond to previously-described bores 60, 62, respectively, in piston 58. Seated in the base of bore 82 is a ball 86 closing off the upper end of bore 84 and corresponding to ball 64 in bore 60. Ball 86 is biased by a spring 88 corresponding to spring 66, which is held in place between a ring 89 and a plug 91 that correspond to ring 68 and plug 70, respectively.

Ports 90, 92 are provided for admitting and exhausting fluid to the head and rod ends, respectively, of the cylinder of ram 40. A bleeder screw 96, which is similar to previously-mentioned screw 78, is provided, which is screwed into a suitable bore in the head end of the rams cylinder.

The cylinders of the rams are so constructed that pistons 58, 80 are permitted substantially the same amount of travel therein between opposite ends of the cylinders.

Considering further details of the hydraulic circuit provided for rams 38, 40, a main control valve is shown at 102 connected with ram 38 through a conduit 104 leading to port 72 in the ram. A conduit 106 connects port 74 of the ram 38 to port of ram 40, and a conduit 108 connects port 92 to valve 102. Conduits 104, 106, 108 are referred to herein, respectively, as first, transfer, and third conduits.

Valve 102 is also connected to a source of hydraulic fluid including a pump 110 and a reservoir 112. The pump has its intake and connected to the reservoir through a conduit 114 and its discharge end connected to the valve through a conduit 116. Reservoir 112 is connected directly to the valve by a conduit 118.

The valve spool of valve 102 is represented in the drawing as an elongated rectangle divided into three squares. The valve spool is adjustable to any one of three positions, and the symbols in each of the various squares indicates how flow takes place through the valve for each of such positions. Thus, with the valve spool in the position illustrated, conduits 104, 108 are closed off where they join with the valve and conduits 116, 118 are connected together through the valve. With the valve spool shifted to the right in the figure, fluid flow takes place as indicated by the arrows in the left square of the valve spool. More particularly, hydraulic fluid is pumped into conduit 104 and exhausted from conduit 108. With the valve spool shifted to the left in the figure, flow takes place as indicated by the arrows in the right square. In this position of the valve spool fluid is pumped into conduit 108 and exhausted from conduit 104. Also shown for the valve are springs represented at 105, 107 which bias the valve spool to the neutral position indicated, and manual means 109, 111 which are actuatable to shift the valve spool.

Further describing the apparatus shown in FIG. 2, it includes means for charging, or filling, the rams with bydraulic fluid. Such means includes a normally closed charging valve 120, a'pair of conduits 122, 124 connecting valve to conduit 104, and a conduit 125 connecting the valve to conduit 106. A spring-biased check valve 126 is connected to conduit 104 by conduit 124, and to conduit 108 by a conduit 128. Valve 126 operates as a pressure relief valve between conduits 104, 108.

Explaining the operation of the pusher apparatus, to fill the rams initially with hydraulic fluid, bleeder screws 78, 96 are adjusted to open the bores that receive them, valve 102 is adjusted to admit fluid under pressure to conduit 104, and charging valve 120 is opened. Under such circumstances, fluid under pressure is introduced into the rams through ports 72, 74, 90.

With bleeder screws 78, 96 open, the space inside ram 38 which is bounded by piston side 58b is vented to the atmosphere, and similarly, the space within ram 40 bounded by side 80a of piston 80 is vented to the atmosphere. With venting, fluid introduced into the spaces is permitted to completely fill the spaces and flush out any air. In this connection, in an actual installation, the two rams are usually disposed horizontally (as shown in FIG. 1), and bleeder screws 78, 96 are located to produce optimum venting, i.e., on the sides of the rams which are on top in the particular installation.

With fluid under pressure introduced into ports 72, 74, '90 piston 80 moves to the rod end of ram 40 with the space inside of the ram bounded by side 80a entirely filling with fluid. Also, despite the fact that hydraulic fluid is supplied simultaneously to both ends of ram 38, since the surface area of piston side 58w exceeds that of side 58b, piston 58 moves toward the rod end of ram 38. The space inside of ram 38 bounded by side 58 fills with bydraulic fluid. All air is purged from conduit 106 and the spaces in the rams vented by bleeder screws 78, 96,

With the pistons thus shifted to the rod ends of the rams, bleeder screws 78, 96 are readjusted to close the bores that hold them, and charging valve 120 is closed. With valve 120 now closed, it will be noted that there is captive fluid in the head end of ram 40 and also in transfer conduit 106. Such captive fluid transfers back and forth between the head end of ram 40 and rod end of ram 38 as the rams are contracted and extended with operation of valve 102.

To contract the rams, valve 102 is adjusted to supply fluid under pressure to conduct 108. Such fluid flows into the rod end of ram 40 causing contraction of the ram, and exhaust of fluid from the head end of the ram through conduit 106 to the rod end of ram 38. Since the eifective piston area of piston 80a is substantially equal to that of piston side 58b, fluid exhausting from ram 40, on contraction thereof, produces simultaneous, like contraction of ram 38. And, on contraction of ram 38, fluid exhausts from the head end of the ram and flows to the reservoir through conduit 104, valve 102 and conduit 118.

According to the invention, the bores and ball pro vided in each piston function to maintain the overall volume of the captive fluid substantially constant, despite the usual expansion and contraction of fluid that occurs with temperature changes. Explaining what takes place when a temperature increase causes the volume of the captive fluid to expand, on extension of the rams, piston 80 reaches the rod end of ram 40 before piston 58 reaches the rod end of ram 38. With piston 80 at the end of its travel, the pressure of captive fluid in the head end of ram 40 increases. When this pressure is sufliciently high (i.e., well above normal operating pressures), ball 86 shifts upwardly against spring 88 and opens the top of bore 84. This permits fluid to flow from side 80a to side 80b of the piston, with piston 58 continuing toward the rod end of ram 38. When piston 58 reaches the limit of its travel, valve 102 is adjusted to its neutral position and the pressure of fluid in the head end of ram 40 drops. Therefore, ball '86 again closes oif the top of bore 84, with the overall volume of the captive fluid again the same as it was when the rams were initially filled with fluid.

In a somewhat similar manner, when leakage or a temperature drop contracts the volume of the captive fluid, on extension of the rams, piston 58 reaches the limit of its travel first. On this occuring, the pressure of fluid in head end of ram 38 increases, and when it becomes sufliciently high, ball 64 shifts upwardly against spring 66 to open the top of bore 62. Fluid then flows from side 58a to side 58b of piston 58 causing piston to continue moving toward the rod end of ram 40. When piston 80 reaches the limit of its travel, valve 102 is adjusted to its neutral position to reduce the pressure of fluid in the head end of ram 38. Ball 64 again closes off bore 62, and the overall volume of captive fluid is adjusted to that which initially existed.

During operation of the apparatus, and more particularly during extension of the rams, should the pressure of fluid in conduit 104 ever get too high, valve 126 opens to provide relief. This further ensures good coordination between the rams whereby skewing in the pusher parts is avoided.

Thus, the invention provides apparatus for automatically producing simultaneous, coordinated operation of a pair of rams. This results from the action of captive fluid transferring between the rod end of one ram and the head end of the other ram as the rams are actuated. With the apparatus herein employed to operate equipment such as load pusher 10, the rams always extend and contract equally during operation, and skewing of pusher member 14, and resultant binding of other parts of the pusher are avoided.

It is claimed and desired to secure by Letters Patent:

1. A load pusher combination comprising a frame, and a pusher member movable relative to said frame,

a pair of fluid-operated rams for moving said pusher member, said rams being disposed with one adjacent one side and the other adjacent the other side of the pusher member, and being operatively interposed between the pusher member and frame,

each of said rams including a piston having means therein defining a passage opening onto opposite sides of the piston, and valve means inhibiting fluid flow through said passage from the rod end to the head end of the ram while accommodating flow in the reverse direction,

the effective piston area exposed to the rod end of one of the rams substantially equalling the effective piston area exposed to the head end of the other ram,

a source of fluid under pressure, and a pair of supply conduits operatively connecting said source to said rams, with one supply conduit connected to the head end of said one ram and the other supply conduit connected to the rod end of said other ram,

2. pressure relief valve operatively interposed between said supply conduits accommodating fluid flow from said one supply conduit to said other supply conduit while blocking flow in the reverse direction,

and a transfer conduit interconnecting the rod end of said one ram and the head end of said other ram.

References Cited UNITED STATES PATENTS 2,261,444 11/ 1941 Neubert 91 -401 2,462,580 2/ 1949 Watson 91411 3,318,199 5/1967 Parrett 91-411 PAUL E. MASLOUSKY, Primary Examiner U.S. Cl. X.R. 9l--415, 422, 451 

